1. Field of the Invention
The present invention relates generally to medical devices and to procedures that use catheters or similar devices. More particularly, the present invention relates to a short sheath designed primarily to facilitate the percutaneous insertion of a catheter and the method of percutaneously inserting such devices using said short sheath. The invention has particular utility when employed to facilitate the percutaneous insertion of balloon catheters, especially intra-aortic balloon catheters (IABs). However, the present invention also may be found to have utility in other medical procedures or applications.
2. Description of the Prior Art
Sheaths for use during medical procedures are well known, particularly for use during percutaneous procedures. As has been well known for many years, catheters, guide wires, or the like, may be introduced into a body channel, such as a vein or artery, through a guide sheath or without a sheath. For convenience, unless the context indicates otherwise, the term "artery" will be used herein in a generic sense to encompass both veins and arteries as well as other body cavities.
Generally, before inserting a catheter into a patient's artery or vein, a hollow needle is inserted through the skin and the subcutaneous tissue until it enters the vein or artery. Especially when an artery like the femoral artery is entered, spurting of blood from the hub at the proximal end of the needle indicates that the needle tip (its distal end) is in the artery. A guide wire is then passed through the needle into the lumen of the artery, whereupon the needle is removed and discarded. A dilator, often with a guide sheath or introducer sheath attached, can then be passed over the guide wire into the artery. A dilator, or a series of progressively larger dilators, are used to enlarge the channel or passageway into the artery so as to facilitate passage of the sheath. Having served its purpose, the dilator is then removed and discarded, leaving the introducer sheath in the artery. The sheath is then pushed further into the artery until sufficiently inserted to serve the purpose. At that point, its distal end is well into the artery, with most of the body of the sheath resident in the blood stream. A catheter can then be inserted into the artery by sliding it through the introducer sheath.
As indicated above, sheaths are well known in the art. For example, one such sheath is disclosed in U.S. Pat. No. 5,167,634 (Corrigan et al.) owned by the assignee of the instant invention. As can be seen, the sheath of the Corrigan reference has, near its proximal end, two wings. Among other functions, those wings limit the insertion of the sheath into the artery. The sheath of the Corrigan reference is a peelable sheath that can be split longitudinally so as to permit removal after it has served its purpose. Perhaps more common are non-peelable sheaths that remain resident in the artery during the entire procedure.
While catheters are frequently inserted through sheaths, it has long been known that they can also be inserted in a sheathless fashion. Each method has its advantages and each has its drawbacks. Use of a sheath provides guidance and a smooth path for the catheter through the skin, the subcutaneous tissue and through a portion of the artery. The sheath, however, when it is resident in the artery is an added obstruction to the flow of blood to the lower extremities and, especially in severely sclerotic or small patients, this obstruction can be of critical importance.
In sheathless insertions, since there is no sheath, there is nothing, except for the catheter itself, to obstruct the blood flow. However, some physicians are reluctant to perform sheathless insertions particularly of relatively large balloon catheters like IABs, because of the resistance often encountered in passing the uncovered balloon through the skin and subcutaneous tissue. The force necessary to overcome that resistance may result in kinking of the guide wire and/or the balloon. The feel of the balloon as it passes through this region is sometimes felt to be a sign of trouble or excessive trauma.